In a background fuser unit that is used for an image forming apparatus, a fuser unit configured to heat a member to be heated by heat from a heating member via a film has been known.
As the fuser unit, a fuser unit having a film guide, which includes a restraining part configured to receive an end portion of the film and to restrain a position of the film, an inner surface guide positioned at an inner side of the end portion of the film and configured to guide rotational movement of the film and a moveable wall configured to be moveable from the inner surface guide in a direction of stretching the film, and configured to press the moveable wall by an elastic member has been known.